Fixed bug in indexing for _polar_weights in CPUSolver
Added getCrossSectionByGroup(int group) routines.  Also changed all the setCrossSectionByGroup(int group) routines to be 1-based rather than 0-based group numbering.
Merge pull request #84 from PrezNattyGibbs/develop

Added getCrossSectionByGroup, etc.
Fixed error checking for getCrossSectionByGroup
Fixed bug in logger set_log_level method when setting base level to SEPARATOR
Fixed bug in use of py_printf as py_print in plotter module
Changed default energy_groups parameter for plotter.plot_fluxes from [0] to [1]
Merge pull request #85 from PrezNattyGibbs/develop

Fixed error checking for getCrossSectionByGroup
Added attribute and method to query Solver class whether CMFD is in use
Fixed bug in 0 indexing for groups in cross-section setters in CMFD. Added CMFD attribute to process.store_simulation_state method.
Made default number of CPU threads to be the CPU count of the host machine
commit before merge